SWARMING OF MALES 123 
then slowly drift towards the ground. Once a pair in copula was seen to issue 
from one swarm and plunge into another swarm close by. The pair made great 
haste to extricate itself while the swarm was immediately thrown into frantic 
excitement and the mosquitoes danced up and down at a furious pace for some 
time, until at last the ordinary measure of speed was regained. With the grow- 
ing darkness the excitement in the swarms increased and the movements became 
more rapid. Few successful unions now took place. Females entering the 
swarm would be pounced upon by two or three males, and together, tumbling 
over each other, they would fall to the ground and there separate. Towards the 
last no more females appeared and with the increasing darkness the swarms 
rapidly diminished, the males flying off into the air. 
“ At 5 o’clock on the following evening the swarms were found as before, 
dancing over every object projecting above the general level. Single mosquitoes 
were seen flying rapidly and straight. These looked larger than the dancing 
males and when captured proved to be females. The air was again very still 
with a current from the south and, as before, the dancing males faced towards it 
and kept on the opposite side of the objects. The west side of the field was 
bounded by tall trees and high up on these, at least fifty feet from the ground, 
before projecting branches, clouds of mosquitoes could be distinguished while 
lower down on these trees there were none. Station was taken at a corn-stook to 
determine how long the dance would continue. As the darkness grew the num- 
bers began to diminish, and at 5.50, when the darkness was almost complete, the 
last male flew away. The departing males flew upward and none of them 
alighted on the stoock. 
“On the fourth evening the field was visited nearly an hour earlier than_be- 
fore. The sun was still shining and there were no mosquitoes present. Later, 
when the sun had disappeared behind the trees, the swarms were again present 
just as on the previous evenings. On this evening, however, there was quite a 
breeze blowing and the mosquitoes could not maintain their position over the 
projecting objects and swarmed altogether on the leeward side of them. Other- 
wise their behavior was much the same, only that the freshening wind occasion- 
ally threw the swarms into confusion and greater activity. Rain and cold 
weather followed the next day and put an end to further observations and pre- 
sumably to the swarming. 
“There are many records of swarms of Culicide and related forms, although 
in many cases there is no exact indication of the identity of the insects in ques- 
tion. I am convinced that all such records, in so far as they refer to swarms of 
the nature described above, apply to Nemocera and probably in every case either 
to Culicidee or Chironomide. I believe that these swarms of dancing males, 
congregated for sexual intercourse, are peculiar to the Nemocera. Many of the 
records from untrained observers, called forth by the appearance of these 
Diptera in extraordinary numbers, though incomplete, are nevertheless of in- 
terest. In nearly all of them the fact that the swarming leads to sexual union 
has been entirely overlooked. 
“ Moufet, in 1634, already speaks of these swarms and notes how they gather 
at the gables of houses and over the heads of people passing over bridges. It 
should be noted that in his chapter ‘De Culicidum’ the Culicids and Chiro- 
nomide are not distinguished, as indeed has been the case with many a writer 
since. 
“The oldest record of the copulation of Culex appears to be that of the 
Spaniard Diego Reviglias, communicated to the Leopold-Carolinian Academy in 
a letter dated 4 March, 1728, but not published until 1737. Reviglias observed 
under the microscope, and described at considerable length, the sexual union 
and the copulatory apparatus of the mosquito. He treats his discovery as a very 
